Nitrogen and ester containing lubricating oil multifunctional viscosity index improver, e.g., viscosity index improver-dispersant, additives have been widely used by the industry. Typically, these multifunctional viscosity index improvers are prepared from a long chain hydrocarbon polymer by reacting the polymer with an acid producing moiety such as acid or maleic anhydride to form the corresponding polymer which is substituted with succinic acid or anhydride groups. Ethylene-propylene has been widely used as the polymer of choice.
High molecular weight ethylene-propylene polymers and ethylene-propylene-diene terpolymers, having viscosity average molecular weights of from about 20,000 to 300,000, are generally produced employing Ziegler catalysts, generally VCl4 or VOCl3 with a halide source, such as organoaluminum halides and/or hydrogen halides. Such high molecular weight EP and EPDM polymers find use as viscosity index improvers. See, e.g., U.S. Pat. Nos. 3,563,964; 3,697,429; 4,306,041; 4,540,753; 4,575,574; and 4,666,619.
The concept of derivatizing V.I. improving high molecular weight ethylene copolymers with acid or anhydride moieties such as maleic anhydride followed by reaction with an amine to form a multifunctional viscosity index improver, e.g., a viscosity index improver-dispersant, oil additive is known in the art as indicated by the following patents.
U.S. Pat. No. 3,316,177 teaches ethylene copolymers of at least 50,000, such as ethylene-propylene, or ethylene-propylene-diene, which are heated to elevated temperatures in the presence of oxygen so as to oxidize the polymer and cause its reaction with maleic anhydride which is present during the oxidation. The resulting polymer can then be reacted with alkylene polyamines.
U.S. Pat. No. 3,326,804 teaches reacting ethylene copolymers with oxygen or ozone, to form a hydroperoxidized polymer, which is grafted with maleic anhydride followed by reaction with polyalkylene polyamines. Preferred are ethylene-propylene copolymers, having M.sub.v from 100,000 to 500,000, prepared by Ziegler type catalysts.
U.S. Pat. No. 4,160,739 teaches an ethylene copolymer (M.sub.v =10,000 to 200,000) which is grafted, using a free radical technique, with alternating maleic anhydride and a second polymerizable monomer such as methacrylic acid, which materials are reacted with an amine having a single primary, or a single secondary, amine group.
U.S. Pat. No. 4,161,452 relates to graft copolymers wherein the backbone polymer is a polymeric hydrocarbon such as EP copolymer or EPDM (M.sub.v =10,000 to 200,000) and the grafted units are the residues of an addition copolymerizable monomer system comprising, e.g., maleic anhydride, and at least one other addition monomer.
U.S. Pat. No. 4,171,273 reacts an ethylene copolymer (M.sub.v =10,000 to 100,000) with maleic anhydride in the presence of a free radical initiator and then with mixtures of C.sub.4 to C.sub.12 n-alcohol and amine such as N-aminopropylmorpholine or dimethylamino propyl amine to form a V.I.-dispersant-pour depressant additive.
U.S. Pat. No. 4,517,104 relates to EP and EPDM viscosity index improver-dispersant additives prepared from EP polymer (M.sub.n =5000 to 500,000), by maleic anhydride grafting and reaction with polyamines.
The following references include disclosures of EP/EPDM polymers of M.sub.n of 700/500,000, also prepared by conventional Ziegler catalysts.
U.S. Pat. No. 4,089,794 teaches grafting the ethylene copolymer (M.sub.n =700 to 500,000) with maleic anhydride using peroxide in a lubricating oil solution, wherein the grafting is preferably carried out under nitrogen, followed by reaction with polyamine.
U.S. Pat. No. 4,137,185 teaches reacting C.sub.1 to C.sub.30 monocarboxylic acid anhydrides, and dicarboxylic anhydrides, such as acetic anhydride, succinic anhydride, etc. with an ethylene copolymer (M.sub.n =700 to 500,000) reacted with maleic anhydride and a polyalkylene polyamine to inhibit cross linking and viscosity increase due to further reaction of any primary amine groups which were initially unreacted.
U.S. Pat. No. 4,144,181 is similar to 4,137,185 in that it teaches using a sulfonic acid to inactivate the remaining primary amine groups when a maleic anhydride grafted ethylene-propylene copolymer (M.sub.n =700 to 500,000) is reacted with a polyamine.
U.S. Pat. No. 4,219,432 teaches maleic anhydride grafted ethylene copolymer (M.sub.n =700 to 500,000) reacted with a mixture of an amine having only one primary group together with a second amine having two or more primary groups.
Related disclosures of maleic anhydride grafted, aminated ethylene-propylene polymer viscosity improver-dispersant additives useful in lubricating oil compositions are contained in U.S. Pat. Nos. 4,507,515; 4,557,847; 4,632,769; 4,693,838; and 4,707,285.
However, these conventional multifunctional viscosity index improvers derived from conventional ethylene alpha-olefin copolymers by such methods as free-radical initiated grafting require relatively harsh reaction conditions in order to graft the acid or anhydride moieties such as maleic anhydride onto the ethylene alpha-olefin copolymer backbone. This may result in economic disadvantages, the formation of deleterious or unwanted byproducts, and incomplete reaction of the ethylene alpha-olefin copolymer with the acid or anhydride moieties (low active ingredient--a.i.). The present invention, by utilizing an ethylene alpha-olefin copolymer having a high degree of terminal ethylenylidene unsaturation, remedies these disadvantages.
U.S. Pat. No. 4,668,834 to Uniroyal Chemical discloses preparation (via certain metallocene and alumoxane catalyst systems) and composition of ethylene-alpha olefin copolymers and terpolymers having vinylidene-type terminal unsaturation, which are disclosed to be useful as intermediates in epoxy-grafted encapsulation compositions.
Japanese Published Patent Application 87-129,303A of Mitsui Petrochemical relates to narrow molecular weight distribution (M.sub.w /M.sub.n &lt;2.5) ethylene alpha-olefin copolymers containing 85-99 mol% ethylene, which are disclosed to be used for dispersing agents, modifiers or materials to produce toners. The copolymers (having crystallinity of from 5-85%) are prepared in the presence of a catalyst system comprising Zr compounds having at least one cycloalkadienyl group and alumoxane.
European Patent 128,046 discloses (co)polyolefin reactor blends of polyethylene and ethylene higher alpha-olefin copolymers prepared by employing described dual-metallocene/alumoxane catalyst systems.
European Patent Publication 129,368 discloses metallocene/alumoxane catalysts useful for the preparation of ethylene homopolymer and ethylene higher alpha-olefin copolymers.
European Patent Application Publication 257,696 A1 relates to a process for dimerizing alpha-olefins using a catalyst comprising certain metallocene/alumoxane systems.
PCT Published Patent Application WO 88/01626 relates to transition metal compound/alumoxane catalysts for polymerizing alpha-olefins.